Hello,
Two scenarios:
1/ If "family route-target" is not enabled, the default RT filter does not exist.
2/ If "family route-target" is enabled and negotiated, the default RT filter is the set of individual /96 RT NLRI derived from locally configured VRF. Specifically, /96 RTs are derived from VRF import policies or "vrf-target|vrf-target import" line(s) of config inside each routing-instance of "type vrf".
You can override/ehnance scenario #2 with locally-configured static RTs to attract inet-vpn routes for VRFs that do not exist locally:
https://www.juniper.net/documentation/en_US/junos/topics/usage-guidelines/vpns-configuring-static-route-target-filtering.html
HTH
Thx
Alex